A method for reconstructing optical properties of diffracting objects by means of a lensless imaging device is known from the article entitled, Lensfree in-line holographic detection of bacteria, Poher et al. In this method, dust particles are placed on the surface of a protective cap, located at about 400 μm from a CMOS (Complementary Metal Oxide Semi-conductor) sensor, the dust particles are illuminated with a spatially coherent light source, and the CMOS sensor measures the intensity of the diffraction patterns corresponding to waves diffracted by the dust particles when they are illuminated. The complex amplitude of the dust particles is reconstructed, according to a reconstruction algorithm, from the measured intensity, the reconstruction algorithm depending on a reconstruction height. The reconstruction height is substantially equal to the height of the protective cap of the CMOS sensor (i.e., substantially equal to the distance between the dust particles and the CMOS sensor along the illumination direction of the particles). However, such a reconstruction method does not allow access to more specific information, notably relating to the structure of the observed particles. Thus, when the observed particles are cells, this method does not give the possibility of distinguishing and viewing the nucleus from the cytoplasm of a single cell.
Thus, a need still exists for a method and system of reconstructing optical properties of diffracting objects, for objects having a diameter of less than 50 μm, notably cells, or colonies of bacteria, giving the possibility of obtaining more specific information on said objects.